The field of the invention relates to engine control systems, including air/fuel control systems having adaptive learning.
Engine air/fuel control systems are known in which fuel delivery to the engine is modulated with a modulation signal having a predetermined amplitude. Such modulation causes engine air/fuel operation to alternate between values which are rich and lean of a desired air/fuel ratio. An air/fuel ratio which averages to a desired value is thereby sought. An example of such a system is shown in U.S. Pat. No. 5,211,011.
The inventors herein have recognized numerous problems with the above approaches. One problem is that the modulation signal amplitude may either be too large or too small to achieve, on average, the desired air/fuel ratio. Another problem is that feedback control is often suspended during such modulation which may result in a degradation in air/fuel operation.